Fuel pump



May 20, 1958' K. J. DICKRELL 2,835,239

FUEL PUMP Filed Feb. 3, 1955 FIG. 3.

INVENTOR. MMNUHJ. DIUY/Pfll ATTORNEY United States Patent FUEL PUMPKenneth J. Dickrell, Chilton, WiS-, assignor to Kiekhaefer Corporation,Cedarburg, Wis.

Application February 3, 1955, Serial No. 485,950 1 Claim. (or. 123-139)This invention relates generally to pumps and more specifically to animproved diaphragm pump for internal combustion engines operating on thetwo-stroke cycle.

One of the requirements of a diaphragm pump for an internal combustionengine is that it produce a substantially continuous flow of liquid at asubstantially constant positive pressure. I-Ieretofore, diaphragm pumpsfor internal combustion engines actuable by the fluid pressureintermittently developed in the crankcase thereof, have developed afluctuating liquid output corresponding to the fluctuations of fluidpressure developed within the crankcase.

It is therefore an object of the present invention to provide animproved diaphragm pump for an internal combustion engine of thetwo-cycle type having a liquid output at a substantially constantpressure.

Another object of the invention is the provision of an improveddiaphragm pump for an internal combustion engine having adjacentchambers exposed to the substantially 180 degrees out of phase crankcasefluid pressure developed in respective adjacent crank chambers.

Another object of the invention is to provide an im proved diaphragmpump for an internal combustion engine of the two-cycle type having agreater liquid pumping capacity for its size than prior known diaphragmpumps.

Another object of the invention is to provide an improved crankcaseactuated fluid diaphragm pump for an internal combustion engine whereinthe liquid output is continuous.

Objects and advantages other than those set forth above will be obtainedfrom the following description when read in connection with theaccompanying drawing, in which:

Fig. 1 is a front elevation view showing the fuel system comprising afuel supply tank, a fuel pump and a carburetor for a two cylinder,two-cycle engine;

Fig. 2 is an elevation view of the engine of Fig. 1 shown partially insection;

Fig. 3 is a section view taken along line 33 of Fig. 1;

Fig. 4 is an enlarged view of the part of the housing of the fuel pumpadapted to be mounted on the crankcase;

Fig. 5 is an enlarged view of the remaining part of the housing of thefuel pump adapted to be secured to the part of the housing of Fig. 4;and

Fig. 6 is a section view taken along line 6-6 of Fig. 1.

As shown in the drawings, a preferred embodiment of this invention isillustrated as applied to a two-cycle internal combustion engine 7. Theengine 7 shown in the drawings includes a crankcase 8 secured to acylinder block 9 and carrying a crankshaft 11. Pistons 12 are eachconnected by a rod 13 with a corresponding crank throw of the crankshaft11 and carried in a correspond ing cylinder 16 of the block 9 foralternate reciprocation. A bearing member. 17 intermediate the crankthrows of the crankshaft 11 divides the crankcase 8 into upper and lowercrank chambers 18, 19 respectively asice 2 sociated with the lower endsof the corresponding cylinders 16. The bearing member 17 includes aninduction passage 21 shown in dotted lines and which opens into chambers18, 19. A carburetor 22 secured to the crankcase 8 includes a mixingpassage 26 which communicates through the crankcase 8 with the passage21 in the bearing member 17 for the delivering of air and carburetedfuel to the chambers 18, 19 in the operation of the engine 7. i

In the operation of the engine 7, the upward stroke of each piston 12compresses the fuel charge in a combustion chamber 23 above the piston12. At the same time, the air and fuel mixture from the curburetorpassage 26 is drawn into the respective crank chambers 18, 19. Duringthe downward power stroke of each piston 12 following ignition of thecompressed charge in the respective combustion chamber 23, the fuel andair mixture in the corresponding crank chamber 18, 19 is compressed fortransfer to a communicating passage 24 shown in Fig. 3 which opensthrough the intake ports 27 above the piston 12 into the cylinder 16.The exhaust ports 28 of each cylinder 16 are controlled by therespective pistons 12 and are uncovered by the pistons 12 for thedischarge of the exhaust through the ports 28 slightly in advance of asimilar opening of the intake ports 27 for the re-charging of thecylinder with fuel and air mixture from the respective crank chamber 18,19 as described. The action of the alternately reciprocating pistons 12produces a constantly changing fluid pressure in the respective crankchambers 18, 19 varying substantially sinusoidally through 360 degreepressure cycles and substantially 180 degrees out of phase with oneanother.

Liquid fuel is supplied to the carburetor 22 by means of a diaphragmpump 29 in which the present invention is embodied having a supply line31 connecting a fuel tank 32 to the inlet of the pump 29 and a conduit33 connecting the outlet of the pump 29 to the carburetor 22. The fuelpump 29 is of the diaphragm type having a housing formed of an uppersection 36 and a lower section 37 with a diaphragm 38 interposedtherebetween. The housing sections 36, 37 may be formed of cast metal orany other suitable material and are provided with openings 39 shown inFigs. 4 and 5 in registry through which bolts 41 are inserted to engagetapped openings,

not shown, in the crankcase 8 to connect the housing sections 36, 37together and mount the pump 29 on the crankcase 8 of the engine 7. Thehousing sections 36, 37 are constructed with recesses 42, 43 and 44, 46therein respectively, each section 36, 37 having a transverse Wallportion extending between such recesses 42, 43 and 44, 46. When thehousing sections 36, 37are connected together, the respective recesses42,. 44 and 43, 46 are in registry forming chambers 47, 48 as shown inFig. 3. The chamber 48 is substantially larger than chamber 47 andconstitutes the primary pumping chamber Whereas chamber 47 functionsprimarily as a surge chamber to provide a smoother or less fluctuableliquid pump output. The diaphragm 38 which is assembled between thehousing sections 36, 37 as shown in Fig. 6 may be in the form of a dischaving a central. portion dividing the chambers 47, 43 and having anouter or marginal portion 49 adapted to be clamped or held between thecooperating portions of the housing sections 36, 37. This diaphragm 38is formed of an elastic, rubher-like material, such as synthetic rubber,or any other suitable elastic substance which will Withstand thedeteriorating effects of gasoline or other liquid fuel being pumped.

An inlet opening 51 and outlet opening 5.2 of the fuel pump 29 shown inFigs. 3, 5 and 6 is formed by the housing section 36 with each opening51, 52 connected to "a respective bore '53, "54 disposed in the lowerportion of the recess 43. Each of the bores 53, 54 is provided with anannular valve seat 56 for mounting a check valve 57. Each of the checkvalves 57 comprises a valve housing 53 having a seatportion matingwiththe valve seat 56 and a valve disc 5'9 urged iuto ,sealingengagement with the valve housing 58 'by means of a spring 61 interposedbetween the valve disc '59 and the valve housing 58 asis well'known inthe art. The check valves 57 are secured tothe housing section 37 bymeans of a clamp plate '62, shown dotted in Pig. '5, which fits over aportion of the valve housing 53 and rigidly clamps the valve 57 to thehousing section 37 by means of screws 63 also shown dotted. The check'valve 57in the bore 53 connected to the inlet opening 51 permitsmovement of the liquid into the recess 43 but prevents the movement ofliquid out thereof into the liquid inlet opening 51 whereas the che'ckvalve 57 in the bore 54 connected to the pump outlet opening 52 permitsliquid-to leave the recess 43 but not to enter'therein through the pumpoutlet opening 52. The housing section 36 is also provided with apassageway 64 shown in Fig. 5 connecting the outlet opening 52 of thepump 29 to the recess 42. The lower section 37 of the housing isprovided with openings 66, 67 as shown in Figs. 3 and 4 leading into therespective recesses 44, 46.

The fuel pump 29 is positionedon the crankcase 8 of 'the engine 7 sothat the openings 66, 67 formed by the housing section 37 are inregistry with corresponding openings 63, 69 as shownin Fig. 3 leadinginto the passages 24 which connect the crank chambers 18, 19. Therefore,the diaphragm .38 dividing the respective chambers 57, 48 will be actedupon by crankcase actuated fluid pressures that are 180 degrees apart;that is, when pressure acting upon the diaphragm 33 of one chamber '47is positive or at the highest value, the pressure acting upon thediaphragm 38 of the other chamber "48 will be negativeor at the lowestvalue.

In operation, movement of the piston 12 downwardly in the upper cylinder16 and upwardly in the adjacent cylinder 16 produces a successivelyincreasing fluid pres sure in the upper crank chamber '18 and asuccessively decreasing fluid pressure in the lower adjacent crankchamber 19. The decreasing fluid pressure in the crank chamber 19 causesthe diaphragm in the chamber 48 to move inwardly drawing liquid throughthe fuel pump inlet opening 51 and check valve 57 into the recess 43.During this action, the outlet check valve 57 is closed. The increasingfluid pressure in the adjacent crank chamber 18 causes the diaphragm inthe chamber 47 to move outwardly expelling the liquid outof the recess42 through the passageway 64 to the pump outlet opening 52. Uponcompletion of the engine cycle with the upper piston 12 moving upwardlyand the adjacent piston 12 moving downwardly, the increasing fluidpressure developed in the lower crank chamber 19 causes the diaphragm 38in thechamber 48 to move outwardly closing the inlet check valve 57 andopening the outlet check valve 57 expelling the liquid from the recess43 through the outlet opening 52. The decreasing fluid pressure in theadjacent chamber 18 causes the diaphragm 38 in the chamber 47 to moveinwardly causing some of the liquid to be drawn into the recess 42. Apush-pull type of pumping action is developed with the surge chamber 47functioning as an auxiliary pump to increase the pump capacity andprovide a pump output that is continuous and at a substantially constantpressure.

Although but one embodiment has been illustrated and described, it willbe apparent to those skilled in the art that various changes andmodifications may be made therein without departing from the spirit ofthe invention or from the scope of the appended claim.

It is claimed and desired to secure by Letters Patent:

A fuel pump for supplying fuel from a fuel source to the carburetor of atwo cycle internal combustion engine, said engine employing crankcaseprecompression and having adjacent crankcase chambers intermittentlypressurized in alternate relation, comprising a first and a secondchamber, a pressure responsive diaphragm extending across each of saidchambers, conduit means connecting the portion of the first chamber onone side of the diaphragm to the fuel source, second conduit meansconnecting said portion of the first chamber with the second chamber andthe carburetor, respectively, valve means controlling the flow of fuelinto and out of said portion of the first chamber in response toactuation of the diaphragm therein, passage means connecting the portionof the first chamber on the opposite side of the diaphragm from theconduit means connections to one of the adjacent crankcase chamberswhereby the inter mittent crankcase pressures serve to flex thediaphragm to pump fuel from the fuel source into the second chamber andcarburetor, respectively, and second passage means connecting theportion of the second chamber on the opposite side of the diaphragm fromthe conduit means connection to the other of the adjacent crankcasechambers whereby the diaphragm in said second chamber is flexedoppositely to the flexing of the diaphragm in said first chamber, saidsecond conduit being open from said valve means to both the carburetorand one portion of said second chamber, .and said second chamber beingsubstantially smaller than said first chamber whereby only a part of thefuel discharge from said first chamber enters said second chamber andthe remainder of the fuel is forced into the carburetor at a time whensaid second chamber is being expanded by the actuation of its diaphragmand the alternating pressures between said first-and second chambersproviding a relatively continuous flow of fuel to the carburetor at arelatively constant pressure.

References Cited in the file of this patent UNITED STATES PATENTS2,713,858 Armstrong et al. July 26, 1955

